Hatching chicks : the third stage of incubation.

This stage of egg incubation is both
exciting and frustrating. You'll be able to see your chick-embryo
moving - and soon after that, you'll be able to see very little. Find
out why.

The candling pictures I use here and in my other hatching chicks series
are my own and follow one of my eggs right through from the start of
incubation to hatching - and beyond. Here's Buffy, the baby who hatched from
this egg, when she was just ten days old.

Days 14 to 19.

Six days, massive growth. This stage of incubation sees the embryo developing all her organs ready for hatching. Here's how she would look if you could see inside the egg during this period.

Exactly what's happening inside the egg?

The start of this stage sees the embryo developing almost all the down it will be born with - the classic fluffy covering you'll see in your own hatchlings.

On days 14 and 15 the chick's skull, beak, claws and scales on the legs all begin to become much firmer and the 'egg tooth', which will be used to break out of the shell, hardens. To help it develop properly the allantois provides a means of calcium being brought from the shell to the embryo - hence the importance of making sure the eggs you incubate are from strong, healthy chickens.

This is what the embryo would look like if you could see inside the egg now. The
amnion is the sac which contains the embryo and protects it until
hatching. The allantois, which as well as providing an exchange of
calcium and oxygen also gets rid of waste, will start to become very
active within the next twenty-four hours.

The air cell is growing to provide enough air to keep the hatchling alive, and the egg white is becoming
smaller. The embryo is now filling most of the egg cavity.

On days 16 and 17 the embryo begins to move itself into position for hatching, tucking its head under its right wing. The renal system begins to produce waste - you'll probably be able to see the remains of this left behind in the egg shell after hatching.

Day 18, and the process of the embryo absorbing the yolk of the egg into its stomach begins. This makes it possible for hatching chicks to survive for up to 48 hours without food or water after it's hatched - they live off the yolk.

By day 19 the process of the embryo absorbing the yolk is speeding up. The chick now fills most of the egg and is ready to start hatching.

Throughout this stage the chick starts to manoeuvre itself
into position for hatching. The head moves underneath the right wing
with the beak pointing towards the air sac. The egg tooth is then in
position to start breaking through the membrane and shell during the final stage.
This is quite an active time and, if you're lucky, you'll be able to see
some movement when you candle the egg.

These two processes of yolk absorption and the beak turning towards the air sac are vitally important. If either one of them is disturbed there can be fatal consequences. It's for that reason that most people favour leaving the egg unturned and not candled after day 18.

At the end of this stage, the chick's ready to begin the process of hatching.

What does candling show us during this stage?

Day 15.

You can see here how the embryo is now filling a large part of the egg. Candling at this point provides a view of the vein - just above the air cell - moving quite energetically as the chick positions itself for hatching. Compare this view with the diagram here.

Day 16.

The embryo is now so big that the top part of the egg looks completely dark and only a few veins are visible at the air cell end.

Day 17.

And only twenty-four hours later, even less can be seen. The chick is now filling all but the very extreme end of the egg.

Day 18.

This picture shows the air cell very clearly but not much else. The air cell by now has grown enough to allow the hatching chick to take its first breath there, and the chick is filling the entire rest of the egg.

Day 19.

There are no further candling photographs after
this point because the eggs need to be left alone so the chicks can
properly position themselves for hatching. They will remain untouched in the incubator until the chicks are hatched and dried.

Just two more days left! Excited? I always am!

Where would you like to go now?

If you want to go through this third stage of hatching chicks again you can go back to the top of the page by clicking here.

Alternatively, click on these pics to go either back to the first two stages of the incubation process, or move on to the final phase of hatching chicks, days 20 and 21.

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This is me! - Certified in chicken welfare & behaviour

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